Furnace construction



Sept. 11, 1962 H. G. POOLE ET AL FURNACE CONSTRUCTION 2 Sheets-Sheet 1Filed Dec. 22, 1959 HllenDHbraham Heru 6.1 0018 P 11, 1962 H. G. POOLEET AL FURNACE CONSTRUCTION 2 Sheets-Sheet 2 Filed Dec. 22, 1959HIIenDHbraham Henry CiPoole NVENTORS Hf? s.

United States Patent Office 3,053,919 Patented Sept. 11, 1962 3,053,919FURNACE CONSTRUCTION Henry Gordon Poole, Golden, Cold, and Allen D.Abraham, Albany, reg., assignors to Oregon Metallurgical Corporation,Albany, Greg, a corporation of Oregon Filed Dec. 22, 1959, Ser. No.861,287 16 Claims. (Cl. 13-8) This invention relates to a novel furnaceconstruction, and more particularly to a furnace for producing within aconfined zone relatively high temperatures. The furnace is characterizedby a number of novel features contributing to easy charging of thefurnace, high thermal efiiciency, close control over operatingtemperatures, ease of repair without extensive shut-down time, controlof atmospheric conditions Within the furnace, etc.

Commonly in various heat-treating processes it is desit-able to producein a thermal reactor relatively high temperature within a confinedtreating zone, and maintain such temperature over long periods of time.Frequently controlled atmospheric conditions are also necessary, asareaction within the furnace may have to be carried out in the presenceof an inert gas, or a gas mixture that excludes gases reactive withmaterial being treated at furnace temperatures. Illustrative of variousapplications wherein the furnace or thermal reactor of this inventionmay be employed are simple heat treatments with helium, hydridingreactions, the Pidgeon process for magnesium, tin reduction of molybdenite, thermal dissociation of molybdenite at high temperatures, andhydrogen reduction of molybdenum oxide. The invention is describedhereinbelow in detail in connection with tin reduction of molybdenitealthough such should not be construed as a limitation in view of thewide range of uses for the furnace partially indicated above.

Furnace constructions are known that comprise furnace walls ofrefractory material defining a furnace chamber and a heater for thefurnace comprising electric re sistance wire Wrapped around the outsideof the filrnace Walls. The resistance Wire is in contact with thefurnace walls and supported thereon. While satisfactory in some uses,the type of construction just outlined has a number of disadvantages.The provision of a heater wire around the outside of the furnace wallsdetracts from the efficiency of heat transfer to the inner furnacechamber. Further, the contact of the heater wire with the furnace wallsmakes necessary long Warmup and cooldown periods, in order to preventexcessive cracking of the furnace walls. In certain applications theheater wire itself frequently will burn out, particularly if certaingases came in contact with the wire to cause oxidation. When such aheater wire fails, its replacement is a lengthy and diflicult operationwith conventional furnace constructions, and almost impossible ifcontrolled atmospheric conditions within the furnace are to bemaintained.

According to this invention, the furnace construction in an embodimentof the invention comprises an elongated, hollow, ceramic member providedwith openings at opposite ends accommodating the circulation of gastherethrough. The interior of the hollow member constitutes a furnacechamber in the construction. A removable electric heater is mountedwithin the furnace chamber, and when this is energized, heat istransferred from the element to the circulating gas passing thereoverand thence to the material being treated. Around the exterior of andadhered to the ceramic member is a covering of a cementitious refractorymaterial that holds the walls of the member in place in the event thatsome cracking of the walls should occur. Around this covering is acovering of insulating material, and the whole is enclosed in a metalshell or casing.

Adjacent an opening at one end of the hollow member (the outlet for thefurnace) and functioning to close it oif whereby controlled atmosphericconditions may be maintained Within the furnace chamber is a condensersection having wall structure defining a condensing chamber thatreceives the gases passing out of the furnace chamber. Similarly,adjacent the other of the openings and closing it off is a chargingsection having wall structure defining a manipulating chamber thatcommunicates with the inner furnace chamber. The heater is proportionedto enable its removal from the furnace chamber through the inlet, andplacement in the manipulating chamber. The furnace is constructed sothat this can be done without opening up the furnace chamber anddestroying any regulated atmospheric conditions set up therein. Thusglove-closed ports are provided that include glove memibers enabling anoperator to reach in from the manipulating chamber and pull anydefective heater from out of the furnace chamber. Once removed, a faultyheater may be replaced using the same ports.

From the above brief introduction it will be seen that faulty elementsmay be replaced rapidly without extensive shutdown time or loss ofatmospheric conditions. Cracking of the furnace walls is minimized, andif such does occur it has little effect on furnace operation. Fastwarmups are possible, as are maximum efliciencies in heat transfer,since heat is generated directly Within the interior of the furnace andthence transferred to the furnace charge.

Thus it is a general object of the invention to provide a furnacewherein relatively high temperatures may be produced within a confinedzone by a heater disposed within the confines of a hollow memberdefining the zone.

Another object is to provide an improved thermal reactor where heatenergy is introduced by heating a circulated gas.

Another general object is to provide an improved furnace having a heaterthat may be easily replaced in case of failure, without disruptingestablished atmospheric conditions.

Another object of the invention is to provide an improved furnaceconstruction having a confined furnace chamber wherein additionalchambers are provided at the inlet and outlet for the furnace chamber,one of which operates to collect and condense reaction products producedin the furnace and the other of which enables re moval of the heaterwithout opening up the interior of the furnace.

Still another object is to provide a furnace construction that includesa furnace shell or casing housing the furnace walls, and wall structurejoined to the shell defining condensing and manipulating chambers,wherein cooling of the casing is effectively done adjacent where suchwall structure joins with the casing.

Still another object is to provide an improved construction for theheater, whereby it is readily moved in and out of a furnace chamber.

Another object is to provide a novel construction for the resistanceelement of an electric heater, whereby it is readily attached anddetached to supply leads therefor.

Another object is to provide a furnace construction wherein amanipulating chamber is included to enable removal of the heater, andwherein means are provided the manipulating chamber accommodating theinsertion of material into the chamber without disrupting atmosphericconditions established therein.

Another object is to provide a furnace that is easily cleaned andinspected between and during intervals of use.

Other objects and advantages are attained by the invention, which isdescribed hereinbelow in conjunction with the accompanying drawings,wherein:

FIG. 1 is a side view of a furnace constructed according to anembodiment of this invention, with portions broken away;

FIG. 2 is an end view of the right end of the furnace illustrated inFIG. 1, also with portions broken away;

FIG. 3 is a section view along the line 33 in FIG. 1; and

FIG. 4 is an enlarged view of the hollow tube that defines the furnacechamber, and a construction for a heater element that is supportedwithin the interior of the furnace chamber.

Referring now to the drawings, and in particular to FIG. 1, the furnaceconstruction shown comprises a central furnace section, indicatedgenerally at 113, including a metal furnace casing or shell 11encompassing a hollow, open-ended ceramic tube or tube portion indicatedat 12 extending through the furnace casing. The walls of tube 12constitute furnace walls defining within the tube a furnace chamber 13.At the charging or inlet end of tube portion 12, or to the right in FIG.1, is wall structure 16 of a charging section defining a hollowmanipulating chamber 15 communicating with inlet 17 of the tube portion.To the left of easing or shell 11 is wall structure 18 of a condensersection defining a hollow condensing chamber Ztl communicating withoutlet 22 of tube portion 12. The furnace construction, comprising thecentral furnace section and the condenser and charging sections may besupported above the floor on suitable frame structure 24.

7 Considering now specific details of construction of the furnacesection, tube portion 12 may be made of alundum or similar materialcapable of withstanding high temperatures. Casing or shell 11 comprisescenter, box-like portion 25 closed off at its ends by opposed end walls26, 28. These end walls are provided with openings 39, 32 that snuglyreceive and thus mount the protruding ends of tube portion 12.Surrounding tube portion 12 is a layer of refractory material at leastpartially comprised of a cementitious material, indicated at 36, andsurrounding the latter and confined within casing 11 is a layer ofinsulating material which may take the form of insulating firebriek,indicated at 38. Layer 36 may take the form of a mixture of alundum andmortar, and is adhered to the periphery of ceramic tube 12, so that thewalls of the tube portion are held in place regardless of any crackingof the tube that may occur by reason of heating and cooling. The wallsof the tube portion, refraetory layer 36, and firebrick insulation 38together provide insulation for the high temperatures generated withinthe furnace chamber.

In the form of the invention shown, end wall 26 of casing 11 is securedin fixed position to center portion 25 as by welding, whereas end wall28 is detachable from center portion 25 to enable repair of the furnacein the event such should be necessary. The connection of end wall 28with center portion 25 is by screw connections 48. As indicated earlier,the furnace is used often under vacuum conditions or under controlledatmospheric conditions. Thus it is important that shell 11 be airtight.To this end, end wall 28 is placed in sealing relationship with box-likecenter portion 25 by O ring seal 50. Cooling of the end wall 28 andbox-like center portion 25 adjacent the location of the ring seal isprovided for by including a tube 52 about the outside of casing 11 forthe circulation of a coolant.

Considering now more specifically the wall structure 18 defining thecondenser section, this comprises an elongated, substantially uprightcasing structure 54 of substantially square cross-section. The casingstructure includes side walls indicated at 55, 56-, 57 and 58. A top 60bounds the top of the casing structure, and at the bottom of the casingstructure is a frusto-pyramidal or hopper portion 62. The walls of thecasing structure are made of metal, and thus have heat dissipatingproperties. In operation of the furnace, hot gases and reaction productsleave furnace chamber 13 and collect in the condenser section where theyare cooled and condensing solids drop to the base of the casingstructure and collect in hopper portion 62. To accommodate removal ofmaterial from the condenser section, the bottom of hopper portion 62 isprovided with an opening 63 normally closed by a cover 64. The latter issecured to the hopper portion as by screw assemblies 66.

Condenser section 18 further includes a view port 7% adjacent the top ofside wall 55. The view port is closed by a cover '72 that includes atransparent window portion enabling the inspection of the interior ofthe condenser section. Cover 72 is secured over the view port by screwassemblies '74. At the top of the condenser section is a light port 76closed by a cover 78 provided with a transparent window section as iscover 72 and secured in place by screw assemblies 80. Completing thedescription of the condenser section, projecting into side wall belowview port is a tube portion 82 integral with the side wall that receivesan elongated rod 84 used in cleaning the interior of furnace chamber 13and positioning a charge in the chamber. A suitable seal (not shown) isprovided between the rod and tube portion 32 whereby the interior of thecondenser section may be maintained sealed off from the outside of thefurnace.

Casing structure 54 of the condenser section is secured to end wall 26of shell 11 by screws 90. Wall 56 of the casing structure has anaccommodating aperture receiving a protruding portion 92 of end wall 26and the outlet end of ceramic tube portion 12. An airtight seal isproduced between side wall 56 and end wall 26 by means of an O ring $1.The walls of shell 11 and the condenser section are cooled adjacent thelocation of the O ring by circulating a coolant through a manifold 96.

Considering now the wall structure 16 defining manipulating member 15,and referring to FIGS. 1 and 2, this comprises top and bottom walls 93,99 and side walls 1%, 191, 132, 1 63. These walls also are metal inorder that heat may be dissipated through the walls. The wall structureis joined to end wall 28 of shell 11 through a sleeve assembly generallyindicated at 196. This includes a sleeve portion 103 integral with endwall 23 and a sleeve portion 11b integral with side wall 1% of structure16. Sleeve portion nests within sleeve portion 108, and an 0 ring 112 isprovided that is clamped between the sleeve portions to seal the twotogether when the sleeve portions are drawn together by means of screws1114. Cooling coils 116 for circulating a coolant extend around theperiphery of sleeve portion 168 and cool the sleeve assembly and the Oring that is part of the sleeve assembly. The coils 116 also aid ininhibiting heat transfer to the manipulating chamber 15.

Wall structure 16 defining the manipulating chamber '15 of the chargingsection further comprises a light port 120 provided top Wall 98 that isclosed by a cover 122 provided with a transparent window portion andsecured in place by screw assemblies 124. Side wall 102 is provided witha sight port 128 closed by cover 13%} and provided with a transparentwindow portion 132. Side wall 1111 is provided a port 136 closed by acover 138 secured by screw assemblies 14!). Cover 133 is provided with atube portion 142 receiving a rod 143. The latter rod is similar to rod84 and is used for positioning a charge within the furnace and forcleaning purposes. Cover 133 also has integral therewith a tube section144 having a cap 146 including a window 145 enabling inspection of theinterior of furnace chamber 13.

An advantage and feature of the furnace construction of the invention isthat a heater may be removed from within the furnace chamber in theevent it need be replaced, with a minimum of shut-down time.Substitution of a new heater for a faulty one is accomplished within themanipulating chamber 15 defined by structure 16.

Thus within the chamber there may be provided a shelf 14-8 to carryspare heaters and repair equipment.

To facilitate the manual removal of a heater from furnace chamber 13 andother adjustments, a pair of gloveclosed port assemblies are included inside wall 132, indicated generally at 150 and illustrated in FIGS. 1, 2and 3. The two are substantially the same in construction and thus onlyone is described. Referring to the figures mentioned, each comprises aport 151, and a flexible glove member 152 of rubber or other syntheticmaterial adapted to receive a persons hand and secured in sealingrelation with an annular flange portion 154 partially defining port 151.Over the outside of flange 154 is a cover 156 which may be secured inclamped relationship over the end of the glove member by screwassemblies 153. Within the interior of manipulating chamber 15 is aclosure plate 160 slidable up and down and guided in guide rails 162.Closure plate 161 is held in a raised position wherein port 151 isopened by a latch ring 164 that fits over a catch 165. Cam 163 is forreleasing the latch ring from the catch (through sharp up and downmovement of plate 160) when it is desired to close port 151. The innerclosure plate confines the glove member from the inside of themanipulating chamber when, for instance, sub-atmospheric pressures arepresent in the furnace. The outer cover 156 is for closing and sealingeach port assembly. When it is desired to manipulate inside themanipulating chamber, the outer covers 156 are detached, a persons handsare inserted in the glove members, the inner closure plates are liftedand latched in place, and the manipulating chamber is then accessibleWithout disrupting any controlled atmospheric conditions existing withinthe furnace. Adjacent bottom wall 99 of wall structure 16 is a loadingassembly, indicated generally at 1761 and illustrated best in FIGS. 1and 2. Specifically, and with reference to these figures, bottom wall 99of the wall structure is provided with an aperture 172 rimed by anangular flange 174. Securedto this angular flange and sealed thereto byseal 1'76 is a cover section 178 provided with a central port 1811.Integral with cover section 178 and at opposite sides thereof extendingdownwardly therefrom are the legs of a U-shaped member 182. These legsthrough their connection with cover section 178 and bottom Wall 99 areheld in fixed position. Alongside each leg is a toggle link mechanism184, each comprising toggle links 184a and 18412. Toggle links 184a,18417 of each mechanism are connected at adjacent ends by a pivotconnection 185. The bottom end of each toggle link mechanism is pivotedadjacent the bottom of a leg of member 182 by a pivot connection 186 andthe top end of each toggle link mechanism is connected by a pivotconnection 187 to a hollow loading bucket or receptacle, indicated at190. Receptacle 1911 has its top placed in sealing relationship withcover section 178 by O ring seal 192.

Port 180 constitutes an entrance port for the manipulating chamber. Theinterior of receptacle 19% opens to port 181). Receptacle 1911 is movedaway from the entrance port when it is desired to place material thereinprior to placing it within chamber 15. Thus a handle portion 194 isconnected to the bottom links 184a of the toggle link mechanisms 134.This handle may be pulled to the left (viewing FIG. 2), with the togglelinks moving from the over-center position shown to an angular positionwith respect to each other, and this movement of the links isaccompanied by movement of bucket 19% downwardly from port 130, to theposition shown by the dotted outline in FIG. 2, where further movementof the receptacle is limited by stop 1% (which is secured to thereceptacle) striking bracket 182. Ears 197 on the handle are providedwith suitable bores receiving studs 198 with the bucket in a raisedposition, and nuts screwed onto these studs secure the bucket in araised position. Within the manipulating chamber, a cover 200 isprovided that is pivoted to the bottom Wall by pivot connections 202.

This cover closes the top of entrance port (thus constitutes a closuremeans for the entrance port), and is sealed to cover section 178 by seal204. Cover 200 is secured in place by wing nuts 206. Note that cover 200may be opened from within chamber 15 with receptacle 1% in operativeposition and secured in covering relation over the bottom of port 131).

The furnace construction of the invention enables the heating ofmaterials under regulated atmospheric conditions. Thus there is providedmeans for circulating specific gases in the furnace, such as an inertgas, hydrogen and the like, and for removing air from the furnace.Referring to FIG. 1, wall structure 16 defining manipulating chamber 15is provided with a conduit 210 connecting with the chamber, and wallstructure 18 of the condenser section is provided With a conduit 212connecting with chamber 21 These conduits may be connected to a suitablecleansing system, in the event that it is desired to recirculatespecific gases in the furnace. Note also that the loading receptacle isprovided with means for purging gas therefrom and for introducing aspecific gas or gas mixture into the interior thereof, by including atthe base of the receptacle conduits 214, 216.

A form of heater means employed for heating the interior of the furnaceis illustrated in FIG. 4. Specifically, and with reference to thisfigure, 220 indicates the heater means generally. This comprises aceramic cylindrical block or mount 222 mounting a pair of elongatedelectrical lead elements or rods, indicated at 224, 226. Ceramic block222 preferably has a cylindrical shield such as shield 22% secured aboutits periphery, to reduce sliding friction between the block and theinner surface of ceramic tube portion 12 during positioning of theheater. The shield and rods are made of suitable metal, and in amolybdenum reduction reaction the shield and rods ordinarily would bemade of molybdenum.

Secured to the left ends of the rods in FIG. 4 is an electric resistanceelement indicated at 232. This may also be made of molybdenum and isbent in the form of a double loop. The resistance element is secured atits ends to the left ends of rods 224, 226 by fitting the ends intoclamp portions 234 of the rods. A central portion of element 232 issupported by fitting it within a clamp member 235 that has an end 235asupported in a tube 236. End 235a is a relatively thin portion curvedsemicylindrically and contacting snugly the inner wall of tube 236, andthus the inner bore of tube 236 is left substantially open whereby gasmay flow through the tube and thence through furnace chamber 13. Aresistance element is detached from block 222 by pulling it on. fromclamp portions 234 and clamp member 235. Power is supplied element 232by flexible conductors 240 and supply conductors 242.

In the reduction of molybdenite in a hydrogen atmosphere, amolybdenite-tin charge may be placed in a boat indicated at 244, shapedas a semi-cylindrical shell open at the top (the side shown in FIG. 4)and closed at its ends. A charge, such as that indicated at 248-, isplaced within the interior of the boat. The charge may take the form ofa sintered mixture of tin and molybdenite shaped as a cylindricalpellet, such pellet having an outer diameter only slightly less than thediameter of the inside of boat 244. Pellet 248 may be provided with acenter bore 250 for the circulation of gas through the center thereof.The boat holds the charge and any part thereof that may melt out ofcontact with the furnace walls defining chamber 13.

Explaining the operation of the furnace in connection with the reductionof molybdenite, a charge is placed in boat 244, and the boat insertedinto chamber 13 using push rod 143. Heater means 220 is then insertedWithin the furnace chamber between the boat and manipulating chamber 15.With the boat and heater positioned, hydrogen may be passed through thefurnace, at a flow rate, for example, of 200' to 300 cubic feet perhour.

7 Current may then be supplied the heater, with temperatures in therange of 15002500 C. quickly obtained, the specific temperatureresulting in a given case depending upon the power input and the rate ofgas flow. The specific flow rate and temperature mentioned are by Way ofillustration.

During the reaction, hydrogen gas flows through the chamber 13, andthrough its heating before reaching the charge, transfers heat from theelectric resistance element to the charge. As heat is applied thecharge, volatile reaction products form, and these are carried off inthe gas stream into condensing chamber 20. While the central ceramictube portion 12 is heavily insulated within casing or shell 11, thewalls 18 of the condenser section dissipate heat and thus the interiorof chamber 20 is substantially cooler than the interior of chamber 13.Reaction products are condensed in chamber 2%, and drop to the hopperportion at the base of the chamber. Hydrogen gas with certain impuritiesis drawn off through conduit 212, whence it may be cleaned andrecirculated.

The manipulating chamber 15, by reason of cooling coils 116 aroundsleeve assembly 106, since it is on the upstream side from the heatermeans, and since its walls also dissipate heat, ordinarily remains atapproximately room temperature. In the event a heater element burns out,the power to the heater may be cut off and the heater removed by pullingblock 222 and the element 2 32 connected thereto out through the inletto tube portion 12. An operator removes the heater by opening thegloveclosed port assemblies 15H and inserting his hands into the glovemembers, which enables him to manipulate within the chamber. A newresistance element is readily positioned on rods 224, 226 and the heatersubsequently inserted into the furnace in an elapsed time of onlyminutes. The furnace then may be started and furnace temperaturesreinstated. Note that throughout the entire operation regulatedatmospheric conditions are maintained, and purging of the furnace afterreplacement of a heater is unnecessary.

It should be noted that the heater is carried out of contact with thewalls of the ceramic tube. This enables fast warmup periods, withoutexcessive cracking of the tube walls. Should some cracking of the tubeoccur, however, the layer surrounding the tube portion containingcementitious material holds the tube portion together and the operationof the furnace is not affected. The entire furnace is sealed, and shouldgases escape into the insulating material, operation of the furnace isnot impaired.

Summarizing important aspects of the invention, what has been disclosedis a thermal reactor wherein heat is introduced to the charge in areaction zone by heating a circulating gas, such gas then traveling overthe charge. The gas may be purified and recirculated. The means forheating the gas in the embodiment shown is a resistance element,although in other embodiments are heaters or other forms of heaters maybe practicable.

Fast reaction rates are possible, because of the type of heat exchangebetween the heated gas and the charge in the reactor. With a constantenergy imput, the rate of gas flow controls the amount of heat transferand the reaction temperature. With a constant flow, gas temperature andreaction rate may be adjusted by varying the energy imput. As acorollary of the above, both the flow of gas and the energy imput may bechanged simultaneously to control temperatures. The provision of meansfor varying the pressure within the furnace or reactor provides anothermeans for varying the rate of reaction within the reaction zone.

It should be noted that the circulated gas may function solely as acarrier, as When an inert gas is used. In some applications the gas mayfunction as a reactant, as in carbon monoxide reduction or hydridingreactions. Certain normally solid reactants may be introduced into thegas stream as a vapor.

While there has been described an embodiment of the invention, and itsoperation in connection with a particular type of reaction, it should beobvious to those skilled in the art that changes may be made in theconstruction and its use without departing from the invention. It isintended not to be limited by the specific embodiment described, but tocover all modifications and variations that would be apparent to thoseskilled in the art and that come within the scope of the appendedclaims.

It is claimed and desired to secure by Letters Patent:

1. A furnace comprising furnace Walls defining a furnace chamber andspaced openings formed in the furnace walls accommodating the flow ofgas therethrough, one of said openings constituting an inlet and theother of said openings constituting an outlet in the furnace, insulatingmeans surrounding the furnace walls, means ad jacent the inlet andoutlet of the furnace chamber closing them off whereby controlledatmospheric conditions may be maintained within the furnace chamber, andmeans for circulating gas through the furnace from said inlet to saidoutlet and heater means mounted within the furnace chamber having a sizesmall enough to enable its removal through one of said openings andoperable when energized to heat the chamber and any gas flowingthereover, said heater means being removable through said one opening.

2. A furnace comprising furnace Walls defining an elongated furnacechamber having openings disposed approximately at either end of thefurnace chamber constituting an inlet and an outlet therefor, andaccommodating the flow of gas through the furnace chamber, insulatingmeans surrounding the furnace Walls, wall structure havingheat-dissipating properties defining a condensing chamber communicatingwith the outlet for the furnace chamber for collecting gas leaving thefurnace chamber and cooling the same, removable heater means supportedwithin the furnace chamber removable through the inlet of the furnacechamber, and wall structure defining a manipulating chambercommunicating with the furnace chamber inlet and proportioned to receivethe heater means, the Wall structure defining the condensing andmanipulating chambers closing off the inlet and outlet of the furnacechamber whereby controlled atmospheric conditions may be maintainedwithin the furnace chamber during operation thereof.

3. A furnace comprising furnace walls defining a furnace chamber forreceiving material for heating and having spaced openings accommodatingthe flow of gas through the chamber, one of the openings constituting aninlet and the other an outlet for the furnace chamber, respectively,removable heater means supported within the furnace chamber andconstructed to be removable from the chamber through one of saidopenings, and means closing oif the inlet and outlet enabling themaintenance of regulated atmospheric conditions within the furnacechamber, said means including wall structure defining a manipulatingchamber communicating with said one opening and proportioned to receivethe heater means .on removal of the same through said one opening.

4. A furnace comprising furnace walls defining a furnace chamber forreceiving material for heating, spaced openings provided the furnacechamber accommodating the flow of gas through the chamber, one of saidopenings constituting an inlet and the other constituting an outlet,removable heater means supported within the furnace chamber andconstructed to be removable through said inlet, and means closing offthe inlet and outlet openings enabling the maintenance of regulatedatmospheric conditions within the furnace chamber, said means includingwall structure defining a manipulating chamber communicating with saidinlet and proportioned to receive the heater means on removal of thesame through said inlet.

5. A furnace comprising furnace walls defining an elongated furnacechamber having openings at opposite ends accommodating the flow of gasthrough the chamber, an

electric heater disposed within the furnace chamber and mounting meanssupporting the electric heater out of contact with the furnace walls,said heater and the mounting means therefor being constructed so as toenable their removal from said furnace chamber through one of saidopenings, Wall structure covering the openings whereby regulatedatmospheric conditions may be maintained in the furnace, said wallstructure including wall structure defining a manipulating chambercommunicating with said one opening and proportioned to receive theheater and mounting means on their removal from said furnace chamber.

6. The furnace of claim 5, wherein said manipulating chamber includesglove-closed ports provided the wall structure defining the chamberequipped with glove members in sealing relation with the wall structureand having interiors open to the outside of the manipulating chamber,said glove members enabling manual removal of the heater and mountingmeans from the furnace chamber.

7. The furnace of claim 5, wherein the manipulating chamber is providedwith an entrance port formed in the wall structure defining the chamberfor placing material in the chamber, closure means for sealing off saidentrance port, and a hollow loading receptacle that in one operativeposition is detachably secured in covering relation over the entranceport, said loading receptacle having an opening that communicates withsaid entrance port in said one operative position, said closure meansbeing openable with said loading receptacle secured in said oneoperative position.

8. The furnace of claim 5, wherein the wall structure covering theopenings includes over the other of said openings wall structuredefining an enlarged condensing chamber having a port accommodating theremoval of material from the condensing chamber and closure means forthe port.

9. A furnace comprising a furnace section substantially enclosed by afurnace shell, said furnace section having furnace walls defining anelongated hollow furnace chamber open at its ends that extends throughthe furnace section between a set of opposed sides of the furnace shell,condenser section and a charging section having walls defining acondensing chamber and a manipulating chamber, respectively, joined tosaid opposed sides of said furnace shell, said condensing chambercommunicating with one open end of said furnace chamber and saidmanipulating chamber communicating with the other open end of saidfurnace chamber, and means for cooling the furnace shell and condenserand charging sections adjacent where the latter two join with theformer.

10. A furnace comprising a furnace section substantially enclosed by afurnace shell, said furnace section having furnace walls defining anelongated hollow furnace chamber open at its ends that extends throughthe furnace section between a set of opposed sides of the furnace shell,a condenser section and a charging section having walls defining acondensing chamber and a manipulating chamber, respectively, joined tosaid opposed sides of said furnace shell, said condensing chambercommunicating with one open end of said furnace chamber and saidmanipulating chamber communicating with the other open end of saidfurnace chamber, sealing means interposed between the condenser andcharging sections and the shell of the furnace section whereby theformer two are in sealing relation with respect to the latter, andcooling means adjacent where the sealing means are located for coolingthe sealing means.

11. A furnace comprising an enlongated hollow member of ceramic materialopen at its ends and having inner walls defining a furnace chamber, arefractory covering about the exterior of the hollow member at leastpartially comprised of cementitious material adhered to the exterior ofthe hollow member, a covering of refractory material about saidfirst-mentioned covering, a metallic furnace shell about saidsecond-mentioned covering, a condenser section and a charging sectionhaving walls defining a condensing chamber and a manipulating chamber,respectively, joined to the furnace shell with the chamberscommunicating with the ends of the furnace chamber, means for coolingthe walls of the furnace shell adjacent where the condensing andcharging sections join with the furnace shell, and means for heating thefurnace chamber, the latter comprising an electric heater disposedwithin the furnace chamber and held substantially out of contact withthe walls defining the chamber.

12. The furnace of claim 11 wherein the electric heater is movable andof a size to accommodate its removal through an open end of the furnacechamber into said manipulating chamber.

13. A furnace comprising furnace Walls defining a furnace chamber forreceiving material to be treated, said furnace chamber having spacedopenings accommodating the flow of gas through the chamber, oneconstituting an inlet and the other an outlet, a heater supported Withinthe furnace chamber movable through said inlet, said heater comprisingan electric resistance element, a support, and electrical leads carryingthe resistance element mounted in said support, means closing off theopenings of the furnace chamber whereby controlled atmosphericconditions may be maintained therein, said means including wallstructure defining a manipulating chamber communicating with said inletproportioned to receive the heater means on its removal through saidinlet, said electric resistance element being easily detached from saidelectric leads.

14. In a furnace, furnace walls defining an elongated hollow furnacechamber with openings at opposite ends, and electric heater means fittedwithin the furnace chamber and removable through one of said openings,said heater means comprising a slidable mount, an electric resistanceheater element, and electric leads completing an electric circuit forsaid heater element supported on said mount, said electric resistanceheater element being detachably connected to said leads and held by theleads out of contact from the walls defining the furnace chamber.

l5. A thermal reactor for heating a charge comprising furnace wallsdefining a furnace chamber having open infeed and outfeed ends, meansfor circulating a gas through the chamber with the gas traveling fromthe infeed to the outfeed end, and means adjacent the infeed end forheating such gas whereby such gas may function as a carrier for thetransfer of heat to the charge, said means comprising an electricresistance heater and leads completing an electric circuit theretosupported within the furnace chamber and substantially out of contactwith said furnace walls.

16. A thermal reactor for heating a charge comprising furnace wallsdefining a furnace chamber having openings at opposite endsaccommodating the flow of gas through the chamber, an electric heaterdisposed within said furnace chamber, mounting means supporting theelectric heater out of contact with said furnace walls and constructedso as to enable removal of the heater from said furnace chamber throughone of said openings, and means for maintaining regulated atmosphericconditions within the furnace and for circulating gas from said inletover said heater and out of said outlet.

References Cited in the file of this patent UNITED STATES PATENTS1,239,178 Grosvenor Sept. 4, 1917 2,325,521 Lambert July 27, 19432,328,479 Mathieu Aug. 31, 1943 2,330,751 Shaub et a1. Sept. 28, 19432,708,156 Paoloni May 10, 1955 2,952,723 Garmy Sept. 13, 1960

